The CCR5 gene encodes a co-receptor for macrophage-tropic strains of HIV-1; in the absence of CCR5, HIV-1 infection is blocked. We propose to render individuals resistant to HIV-1 by targeted inactivation of the CCR5 gene in the progenitor cells of macrophages. We describe a method for the development of a targeted methyltransferase that will give strong and enduring inhibition of CCR5 gene expression. DNA methylation is responsible for the transcriptional repression of transposable elements and genes subject to X inactivation or genomic imprinting. Methylation patterns are replicated along with the DNA during S phase. Transient presence of a sequence specific methylating agent will give enduring inactivation of the target gene. We will develop DNA methyltransferases specific to the CCR5 promoter by fusion of CpG-specific DNA methyltransferases to zinc-finger proteins designed to bind to the proximal promoter of the CCR5 gene. The procedure involves rational design and selection of novel zinc finger proteins. The ultimate goal of the project is the development of a recombinant adeno- associated virus (AAV) that can deliver a targeted methyltransferase to selectively inactivate the CCR5 gene in the target cell populations. The strategy developed here will find broad application in other disease therapies. PROPOSED COMMERCIAL APPLICATION: Targeted methylation of the CCR5 gene will render individuals resistant to HIV infection. This will have an immediate impact on HIV therapy and the prevention of infection. The broader potential application of this research is to selectively repress any human or viral gene implicated in human disease, thus creating a new class of therapeutic agents.